Configuration data type of nginx

Is there any specific name of the data format used by nginx? For example:

upstream app1_upstream {
    server app1:80;
}
server {
    listen 80;
    server_name app1.example.com;

    location / {
        proxy_pass http://app1_upstream;
    }
}

This file looks very much like a type JSON , more obviously it is not.